Spindle/Z Slider dropping / Spindle drop down on Poweroff/Estop (Elite Series)

Correct, but I wanted a replacement for my stepper motors (not original) which are 420 oz-in.
After some searching I found a Nema 23 with brake that had 3 N.m holding torque.

Just replying on the spindle question, yes, the E-stop does stop the HY VFD, but I don’t have a breaking circuit, so it takes about 5 seconds (no load) for the motor to spin to a stop.

As for me, I have moved on about the drop. I just ensure there is no bit from the day before and power up with the E stop cycle, and if it drops, no harm, no foul. I then load a 1/4 endmill for probing, etc. and continue my day. I was thinking, I could put a short 2x4 on edge under the Z axis, as it would be quicker to power up, as rarely do I have a bit longer than 3 1/2 inches extension, but most of this is getting used to the differences from my journeyman with the buildbotics.

Jim, this was my exact question as well. I don’t understand if there is power to it why is it still falling. I don’t really want to start adding extra things like a electro mag brake. I think I’ll contact masso and see what they think.

There is an enable pin on the stepper motor, if you e-stop the controller it cuts the signal (24v?) to the enable pin on all 4 stepper motors and they effectively power off at that point (even though they still have 36v to them). This is intended to be a safety feature to stop all motion of the motors - however it seems to be causing motion due to the loss of holding torque :wink:

Is there a way to disable the z estop? Or keep power on it some how? This seems to be a common problem in the cnc community

I don’t have the Elite series, I have converted my Journeyman to Masso G3 with a Gecko G540 stepper motor driver which are the default open loop motors. I do not use the enable pin to kill the G540 on e-stop which means any time the machine is on the axis is enabled (and therefore not considered rendered safe as any errant step signal would cause it to move). You could do the same for your Z axis so it doesn’t drop on e-stop however if you power it off then of course it would lose power and holding torque hence why the brake is considered a better option.

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Disabling the E stop in my opinion is not the best option - for safety reasons - but as @WaywardWoodworker mentions it is often done but I think by experiences users who know and manage the risks. It was also mentioned that the problem does not go away, since on shut down the detent torque of the motor is not sufficient to counter gravity.

I decided to invest in a new motor with electric brake for this reason, I it was certainly worth it to me for the piece of mind. It does add cost, and some complexity as the break needs to be powered and controlled through a relay - I happened to have both as I built my own system around a Woodworker and Masso G3.

I believe closed loop steppers with integrated brakes are available with appropriate torque values, or there is also a Nema 23 adapter available.

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Hey Folks,

As the guy that started this thread, I’d like to “bail” back in with some thoughts. Firstly, I discovered that hitting the E-stop during start up (sometimes, maybe 25% of the time) allowed the Foreman Elite Z axis to drop until it contacted something, a “freefall, if you will”, again it’s a 2.2Kw spindle that is somewhat heavy. While doing a 5 hour carve, and needing lunch away from my shop, I hit the “red” stop button on the bottom of the Masso while it was in a rapid reposition and stopped the spindle manually. After nearly an hour, I started the spindle again and hit the green start button, resuming the carve. All was well overall, and the file finished as you might expect.

So, thinking about it, using the red stop button as an E-stop without the Z axis dropping “is” possible. Now, before you lose focus, you can set the spindle to auto-stop if you hit the red stop button (in case you didn’t know, it is an option in the spindle setup page), and as I see it, is essentially the same at least in my set-up as using the E-stop. It immediately stops the X,Y,Z motors where they are and auto-stops the spindle, if selected.

So, even though I have started a rather contentious thread that has headed in many directions, perhaps I have also found an easy solution. BUT!, in my opinion, that should have been the workings with the E-stop in the first place. In my opinion, this could be fixed with firmware change, but I’m not a programmer. I will try it at my shop tomorrow, but I’m pretty sure it will work for both the spindle folks and the router folks as well, but again, I don’t have the router in my case. I promise to follow up with what I find out.

I’m a simple guy. When I upgraded to the Z-20 Z axis and realized the weight of the 2.2kw spindle was enough for it to drop the Z axis down when power was off I added a spring to counter the weight. It’s not a strong spring but it’s more than enough to counter enough of the weight of the spindle.

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any chance you have a photo?

I currently have it taken apart right now as upgrading to the Z-20 axis means I have to modify my dust boot. Hopefully I’ll be putting it back together this weekend.

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I find it odd that some drop and some do not, I have a 2.2 Spindle and it does not drop when powered off but rather it is a little difficult to move it up or down in the unpowered state.
Pat

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Hey Jim, hey all,

I have no experience with the Masso controller so I don’t know which type of Emergency Stop it provides.

But the manufacturer of a machine (an entire machine, not the manufacturer of only a machine controller), in order to provide safety, has to implement the emergency stop type that is suited to meet the hazards that can occur during the operation of the machine. Such emergency stop standards are defined in IEC 60204-1. The updated version distinguishes between emergency stop and emergency power off. And cutting electricity from a device is only recommended when it is necessary.

There exists different stop categories. The most known is STO (Safe Torque Off). This is a category 0 emergency stop and it means that the power is cut from a motor so it immediately can no more exert any torque. VFDs are usually certified to provide the safety of STO when their STOP command is active – which is the reason why it is safe to change the bit in the collet with the VFD just in STOP mode.

But when you have STO as emergency stop on your CNC machine and subsequently on your milling motor, this does not mean that the motor really stops to turn immediately. It just means that it gets its power cut. A high-speed induction motor (that has no brushes) like a spindle may only come to a standstill after minutes. STO also means that the brake function of the VFD is not used, the spindle is simply left coasting.

With the stepper motors of a CNC machine, the situation is even worse if you just have STO as emergency stop mode: Today stepper motors are hybrid motors which mean their permanent magnets are usually not strong enough to hold a mechanical load when their power is cut and they loose their electromagnetic detent. What makes a stepper hold its position (and therefore enables the machine to enter a safe mode with no more parts moving e.g. when the door of your CNC machine is opened) is the holding torque, which can only be present if the stepper motor is still controlled by the controller and is provided with electric current and controlled by the loop.

Therefore IEC 60204-1 defines many more stop categories. A Safe Stop 1 (SS1) is defined as first bringing the machine to a controlled standstill, and only then enter STO (Safe Torque Off), which means powerless mode in the end, which prevents any torque being exerted. It first stops all motion before it enters the power cut mode. However this is still not the right stop category for a stepper motor, since it is still left powerless and may passively start to move by a load through gravity. Think of a robot arm, or a crane with a load on it. You don’t want it to let go of everything in case of an emergency, as this would be much too dangerous, just as you don’t want your heavy spindle to come down when emergency stop is pressed and makes a nice hole into your table or breaks the bit. It is clear that a stepper motor that receives no more power can not exert any torque, but it is also clear that because it looses its electromagnetic detent, it can start to passively move by the weight of a load attached to it, just like the load on a crane or, when thinking of a robot arm, by its own weight. Therefore you would need to have a Safe Stop 2 (SS2) mode, which brings the stepper motors to a controlled standstill and then maintains the power and the control by the controller in order to provide the holding torque to ensure the machine will not move anymore.

There are even more safety stop modes defined in IEC 60204-1. If someone is interested in the topic, search for “stop category” and “60204-1” in a WWW search engine to read more about it.

So when you design a machine that has moving parts, you have to choose the correct emergency stop category by thinking of all types of hazard that could occur.

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I don’t think you understand, the E-stop situation is during boot up and is not optional. In order to use the machine, you must cycle the E-stop as the first thing in power on, otherwise nothing is functional.

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I’m mostly concerned about after a power down and it dropping. If moving the motors while it’s off is bad, i don’t see how turning it off, and it dropping could be good.

(Titled - Support: Tightening a loose bottom z wiper on the Onefinity CNC)
I have an elite and tightening the grub screws slightly on both top and bottom solved my spindle drop problem…the washers were properly seated, so I just tightened the screws. The YouTube from Onefinity support( link above) shows how to access the screws…the video is for the 1st gen z slider…but it’s the same procedure for the heavy duty z slider on the elite.

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I tightened mine too, but the weirdest thing… it dropped when i hit home after turning it on.
I hit the estop, released, and when i hit home is when it fell…

I really am wanting a compatible z motor with a brake but i haven’t found one

What is the criteria you have for compatibility?

Ultimately that it’ll work and the reason i bought the elite almost exclusively was because of the closed loop motors.

I figure $400 delivered is pretty reasonable for budget.

I’m also upgrading my Nighthawk to pwncnc v4 hoping the reduced weight of the 4" hose will limit the free fall it does unpredictably

Perhaps one of the brake adapters that couple between the Masso motor and z ballscrew might be the easiest to implement. It would fit in your budget as well. Shaft size differences may be the only issue with this solution.

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